Certain 2-(hydroxyalkyl)-2,5-dialkyl-4-hydroxy-4,5-dihydrofuran-3-ones and method for their preparation

ABSTRACT

Addition compounds of 2- or 5-monoalkyl and 2,5-dialkyl-4-hydroxy-2,3-dihydrofuran-3-ones and C 2  -C 9  carbonyl compounds are provided. These addition compounds are useful to impart improved flavoring properties to foodstuffs.

This application is a continuation application of U.S. application Ser.No. 488,631, filed July 15, 1974, now abandoned, which, in turn, is adivisional application of Ser. No. 378,085, filed July 11, 1973, nowissued as U.S. Pat. No. 3,950,565.

BACKGROUND OF THE INVENTION

It has been proposed to incorporate certain furenidones, i.e.4.hydroxy-2,3-dihydrofuran-3-ones with two alkyl substituents in the 2-and 5-positions, into foodstuffs in order to improve their flavouringproperties. It was found, however, that these compounds are not quitestable under certain conditions. The problem arises particularly whenfoodstuffs containing the furenidone, in particular a2,5-dialkylfurnidone, are stored for a prolonged time or when heatingwhen preparing the foodstuff is necessary.

SUMMARY OF THE INVENTION

The invention relates to a chemical process for preparing novel chemicalcompounds, to the compounds pre se and a process for improving theflavouring characteristics of foodstuffs by incorporating the novelcompounds and to the foodstuffs thus obtained.

It has now been found that addition compounds of mono- ordialkylfurenidones and carbonyl compounds such as aldehydes and ketonescan be conveniently prepared and that these compounds -- which arestable upon storage -- under suitable conditions, especially uponheating, revert to the free furenidone and that they therefore areexcellent precursors of the furenidones which can advantageously beincorporated in foodstuffs.

DETAILED DESCRIPTION

The flavour precursors of the present invention are derived from afurenidone and a carbonyl compound, both of which possess valuableflavouring properties.

The nature of the carbonyl compound determines whether the precursorreverts under mild or under more severe conditions to the flavouringfurenidone.

Under acid or neutral reaction conditions the following additionreaction of the furenidone takes place: ##STR1##

In this general formula R¹ and R² represent a lower C₁ -C₄ alkyl group,preferably methyl or ethyl, while R³ represents hydrogen or a methylgroup and R⁴ represents hydrogen or an organic radical consisting of1-14 carbon atoms, hydrogen and 0-2 oxygen atoms, preferably ahydrocarbyl, more in particular an alkyl group or alkenyl groupcontaining 2-10 carbon atoms. Furthermore, in case R³ represents amethyl group, R⁴ should not contain more than 4 carbon atoms. Thesenovel carbonyl addition compounds occur in two stereoisomeric forms incase R³ and R⁴ represent different groups and both forms are suitableflavour precursors for the purpose of this invention.

Particularly preferred carbonyl compounds which can be added to thefurenidone are aliphatic saturated and unsaturated aldehydes andmethyl-ketones such as acetaldehyde propanal, octanal, acetone,methylethylketone, cis-3-hexenal and cis-4-heptenal. Aromatic andheterocyclic aldehydes such as phenylacetaldehyde, benzaldehyde,furfuraldehyde, methylfurfuraldehyde and hydroxymethylfurfuraldehyde,can also be used. Carbonyl compounds containing 6-8 carbon atoms arepreferred.

The addition reaction takes place smoothly in a suitable polar solventsuch as water in the presence of an acid-base catalyst under neutral oracid conditions at room temperature although higher -- up to 100° C --and lower temperatures, above 5° C, can also be used. Atmosphericpressures are suitably employed. However, too high temperatures favourreversion.

The novel addition compounds of the alkyl substituted furenidones can beisolated without undue difficulties and may be used according to thepresent invention for incorporation into foodstuffs, in particular infoodstuffs which are heated to temperatures over 100° C when beingprepared for consumption. Such foodstuffs are e.g. shortenings, fats,margarines, especially bakery frying margarines, dried sterilised ordeep-frozen soups, meat products, meatballs, ready-made meals, meatimitating products such as those known as texturised vegetable protein,mesophase, and various products used in bakeries, e.g. reinforced flour,baking aids etc. The amount of addition compound incorporated into thefoodstuff ranges from 0.1-500 parts per million, dependent on theparticular precursor and foodstuff, preferably 1-100 ppm.

Incorporation into the product may take place by adding the additioncompound to the ingredients, spraying over the formed products etc. Theaddition compounds are usually used in conjunction with furtherflavouring agents or precursors thereof, such as e.g. amino acids,nucleotides, carboxylic acids, sweetening substances, etc. Of course theactual combination is determined by the type of product.

By way of illustration the following Examples are given to elucidate theinvention:

EXAMPLE I

2-(1-hydroxyethyl)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone was preparedas follows:

In a round-bottomed flask equipped with a stirrer and a condensor, 12.8g (0.1 mole) of 2,5-dimethyl-4-hydroxy-3-(2H)-furanone and 44 g (1.0mole) of acetaldehyde were introduced into a solution of 3.0 g of oxalicacid in 100 ml of water. The mixture was stirred and refluxed for 1hour. After cooling, the mixture was extracted 5 times with 25 mlportions of chloroform and the organic solvent was evaporated off. Theresidue was purified by chromatography on 50 g of polyamide. Afterelution by means of a 50/50 mixture of ether and petroleum ether, 9.4 gof the title compound was obtained (which corresponds to a yield of54%). Recrystallization from ether gave the pure product with m.p.112°-144° C).

Infrared absorptions (in KBr disc.) were at 3400, 3200, 1697, 1610,1450, 1370, 1250, 1072, 1066, 1005 and 924 cm⁻¹.

The NMR spectrum [in CDCl₃, internal standard Si(CH₃)₄ ] had signals atδ = 1.17 (doublet), δ = 1.41 (singlet), δ = 2.27 (singlet), δ = 3.81(quartet), 4.3-5.7 (broad peak).

The mass spectrum showed peaks at m/e 172, 157, 155, 154, 128, 101, 85,83, 72, 45, 43.

50 mg of the compound thus obtained was heated in 0.5 ml of water to atemperature of 100° C. The breakdown of the compound into2,5-dimethyl-4-hydroxy-3-(2H)-furanone and acetaldehyde was followed byinvestigating the n.m.r. signals at intervals. In particular thediminishing signal of the starting compound at 0.99 ppm (with respect todimethylsulfoxide) and the increasing signals of2,5-dimethyl-4-hydroxy-3-(2H)-furanone at 1.25 and 2.08 ppm werefollowed. The other signals present in the spectrum recorded in CDCl₃solution are obscured by the water signal. From the change in signals itwas deduced that after about 48 hours 50% of the starting material hadbeen converted into the 2,5-dimethyl-4-hydroxy-3-(2H)-furanone. In anaprotic solvent 50% was converted within a fraction of an hour to 24hours, as a similar experiment showed, whereas at 160° C 50% wasconverted in 1/4 hour.

EXAMPLE II

2-(1-hydroxybenzyl)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone was preparedas follows:

A mixture of 5 g of 2,5-dimethyl-4-hydroxy-3-(2H)-furanone and 10.6 g ofbenzaldehyde was added to a mixture of 20 ml of water, 20 ml of dioxanand 0.5 g of oxalic acid. The mixture was then refluxed for 4 hours,cooled and extracted with chloroform. The chloroform extract wasevaporated and the residue purified by column chromatography overpolyamide using ether -- light petroleum 50/50 as the eluent; 2.7 g (30%yield) of the title compound was obtained which was recrystallized fromchloroform, m.p. = 122°-124° C.

Infrared absorptions (KBr disc.) were at 3400, 1715, 1635, 1455, 1370,1240, 1096, 1080, 1042, 1010, 910 and 705 cm⁻¹. The NMR spectrum[solvent CDCl₃, internal standard Si(CH₃)₄ ] had signals at δ = 1.22(singlet), δ = 2.17 (singlet), δ = 4.73 (singlet), δ 4.9-5.6 (broadpeak), δ = 7.15 (singlet).

The mass spectrum showed peaks at m/e 234, 128, 107, 106, 105, 85, 77,57, 55, 52, 51, 50, 45, 43.

EXAMPLE III

2-(1-hydroxy-2-phenylethyl)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone wasprepared as follows:

To a mixture of 6 g (0.05 mole) phenylacetaldehyde and 1.28 g (0.01mole) of 2,5-dimethyl-4-hydroxy-3-(2H)-furanone was added 60 mg of boricacid and the mixture was stirred at 80° C for 3 hours. After working upthe reaction mixture as described earlier, 0.57 g (23%) of the titlecompound was obtained, with melting point 157.5°-159° C.

Infrared absorptions (KBr disc.) were at 3500, 3240, 1697, 1616, 1447,1298, 1240, 1097, 1058, 746 and 703 cm⁻¹. The NMR spectrum [solventDMSO-d6 + CDCl₃ (3:2), internal standard Si(CH₃)₄ ] had signals at δ =1.32 (singlet), δ = 2.15 (singlet), δ = 2.35-2.62 (multiplet), δ = 3.60(multiplet), δ = 5.00 (doublet, δ = 7.00 (singlet), δ = 7.98 (singlet).

The mass spectrum showed peaks at m/e 248, 230, 205, 157, 128, 121, 120,111, 103, 101, 91, 77, 43. The addition compound in an aprotic solventwas converted for 50% to 2,5-dimethyl-4-hydroxy-3-(2H)-furanone afterheating for 1/3 hour at 160° C.

EXAMPLE IV

0.3 g of 2-(1-hydroxyethyl)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone wasadded to 1000 g of unflavoured margarine and the mixture then heated ina pan for 5 minutes at 160°-170° C. This flavoured fried margarine waspreferred to a fried margarine without addition by 8 out of 11 tasters,who mentioned particularly its sweet, caramel-like aroma.

EXAMPLE V

To 100 g of hardened fat 5 mg of2-(1-hydroxyethyl)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone was added andthe mixture was then heated for 5 minutes at 150° C. This fat waspreferred to a fat without addition by 9 out of 10 tasters who mentionedparticularly its mild fruity aroma.

EXAMPLE VI

A basis for canned beef soup was prepared by adding the followingingredients to 4 liters of water:

    ______________________________________                                                         grams                                                        ______________________________________                                        Noodles            160                                                        Herb and spices    1.6                                                        Tallow             80                                                         Vegetables         400                                                        Monosodium glutamate                                                                             16                                                         Protein hydrolysate                                                                              16                                                         Meat extract       16                                                         Salt               64                                                         Raw meat           400                                                        ______________________________________                                    

The total amount was divided into two portions of each 2 liters; 0.08 gof 2-(1-hydroxyethyl)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone was addedto one of the portions. The second portion, which was used withoutfurther addition, served as a comparative example. The mixtures thusobtained were canned in half liter tins and sterilised in an autoclavefor 1 hour at 120° C. A soup ready for consumption was prepared byadding an equal volume of water to the contents of each tin. Afterheating the soups were tested and a majority of the flavour evaluationpanel preferred the soup with the added flavour precursor because of itsmore pronounced meaty flavour.

EXAMPLE VII

A shortcake dough was prepared with the following ingredients:

    ______________________________________                                                       grams                                                          ______________________________________                                               Flour     450                                                                 Sugar     225                                                                 Fat       250                                                                 Water      65                                                                 Salt       5                                                                  Baking powder                                                                            3                                                           ______________________________________                                    

The fat and the sugar were mixed in a Hobart mixer (Type: CE 100) for 3minutes at speed 2. After adding the water, mixing proceeded for another2 minutes. Subsequently the flour, the salt and the baking powder wereadded, after which the composition was mixed for 10 minutes. The doughwas spouted on baking trays in the shape of piped shortcakes and bakedfor 20 minutes at 180° C. In an analogous way piped shortcakes wereprepared in which, however, 20 mg of2-(1-hydroxy-2-phenylethyl-2,5-dimethyl-4-hydroxy-3-(2H)-furanone wereadded to the dough. The shortcakes thus prepared were evaluated by apanel in a pair test. The shortcakes to which2-(1-hydroxy-2-phenylethyl-2,5-dimethyl-4-hydroxy-3-(2H)-furanone hadbeen added were generally preferred by the members of the panel.

EXAMPLE VIII

A mixture of 10 g of 2,5-dimethyl-4-hydroxy-3-(2H)-furanone, 20 ml of a37% formaldehyde aqueous solution, 50 ml of water and 0.7 g of oxalicacid was stirred for 18 hours at room temperature. After working up thereaction mixture, the crude reaction product was purified by columnchromatography over polyamide. Elution with pentane-dichloromethane80/20 yielded the pure2-hydroxymethyl-2,5-dimethyl-4-hydroxy-3-(2H)-furanone, which wasrecrystallized from ethyllactate m.p. 124°-125° C.

Infrared absorptions (KBr disc.) were at 3360, 3170, 1693, 1675, 1607,1596, 1465, 1300, 1280, 1236, 1220, 1160, 1085, 1050, 1000, 950, 905,850, 770, 605, 552, 506 and 397 cm⁻¹.

NMR spectrum [DMS0-d6 (dimethylsulfoxide, containing 6 deuterium atomsinstead of hydrogen), internal standard Si(CH₃)₄ ] had signals at δ =1.25 (singlet), δ = 2.13 (singlet), δ = 3.42 (broad signal), δ = 5.0(broad signal), δ = 8.1 (broad signal).

The mass spectrum showed peaks at m/e 158, 141, 140, 128, 127, 115, 101,97, 85, 69, 43.

EXAMPLE IX

To a mixture of 1.0 g of 2,5-dimethyl-4-hydroxy-3-(2H)-furanone, 5 g ofpropanal and 20 ml of water were added 0.2 g of oxalic acid and themixture was stirred at room temperature for 25 hours and then extractedthree times with chloroform. The chloroform extract was evaporated andthe residue purified by column chromatography on polyamide usingether-pentane 10/90 as the eluent. Pure2-(1-hydroxypropyl)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone was obtained,which was recrystallized from ether-pentane 50/50; solid mass at roomtemperature.

Infrared absorptions (KBr disc.) were at 3380, 3200, 1695, 1617, 1460,1440, 1380, 1370, 1365, 1295, 1254, 1215, 1084, 1078, 1009, 973, 948,731 and 570 cm⁻¹.

NMR spectrum [DMSO-d6, internal standard Si(CH₃)₄ ] had signals at δ =1.25 (singlet), δ = 2.10 (singlet), δ = 3.26 (multiplet), δ = 4.92(doublet), δ = 8.03 (singlet), δ = 1.25 (multiplet), δ = 0.90(multiplet).

The mass spectrum showed peaks at m/e 186, 157, 128, 101, 97, 85, 69,57, 43.

EXAMPLE X

Example IX was repeated except that in this instance the propanal wasreplaced by 5 g of butanal. From the reaction mixture2-(1-hydroxybutyl)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone was isolatedwith m.p. 103°-104.5° C.

Infrared absorptions (KBr disc.) were at: 3490, 3150, 1690, 1618(sh),1609, 1462, 1435, 1365, 1340, 1272, 1245, 1222, 1090(sh), 1075, 1050,1005, 982, 984, 855, 760, 745, 720, 689, 607, 595 and 586 cm⁻¹.

NMR spectrum [DMSO-d6, internal standard Si(CH₃)₄ ] had signals at: δ =1.20 (singlet), δ = 2.05 (singlet), δ = 3.30 (multiplet), δ = 4.82(doublet), δ = 7.85 (singlet), δ = 1.0-1.5 (multiplet), δ = 0.80(triplet).

The mass spectrum showed peaks at m/e 200, 157, 139, 128, 111, 101, 85,72, 71, 57, 43.

EXAMPLE XI

Example IX was repeated, except that in this instance the propanal wasreplaced by 6 g of octanal. From the reaction mixture2-(1-hydroxyoctyl)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone was isolatedwith melting point 97°-98° C.

Infrared absorptions were at (KBr disc.): 3495, 3180, 2960, 2920, 2860,1690, 1618, 1610, 1460, 1436, 1365, 1335, 1260, 1245, 1205, 1070, 1005,972, 945, 760, 722 and 578 cm⁻¹.

NMR spectrum [solvent DMSO-d6, internal standard Si(CH₃)₄ ] had signalsat: δ = 1.25 (singlet), δ = 2.10 (singlet), δ = 3.30 (multiplet), δ =4.93 (doublet), δ = 8.00 (singlet), δ = 1.20 (multiplet), δ = 0.85(triplet).

The mass spectrum showed peaks at m/e 256, 195, 167, 130, 129, 128, 85,84, 82, 81, 57, 43.

EXAMPLE XII

Example IX was repeated, except that in this case the propanal wasreplaced by 4 g of cis-4-heptenal. After column chromatography of thereaction mixture the pure2-(1-hydroxy-4-cis-heptenyl)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone wasisolate.

Infrared absorptions (KBr disc.) at: 3480, 3200, 3005, 1695, 1615, 1458,1435, 1370, 1336, 1249, 1240, 1083, 1070, 1004, 935, 760, 720, 685 and575 cm⁻¹.

NMR spectrum [solvent DMSO-d6, internal standard Si(CH₃)₄ ] had signalsat: δ = 1.21 (singlet), δ = 2.05 (singlet), δ = 3.40 (multiplet), δ =4.90 (broad signal), δ = 7.90 (broad signal), δ = 1.2-1.5 (multiplet), δ= 1.7-2.2 (multiplet), δ = 5.15 (multiplet), δ = 0.89 (triplet).

The mass spectrum showed peaks at m/e 240, 222, 179, 151, 129, 128, 95,85, 84, 83, 69, 68, 57, 55, 43.

EXAMPLE XIII

Example IX was repeated, except that in this instance the propanal wasreplaced by 5 g of furfural. From the reaction mixture2-(1-hydroxymethylfuran)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone wasisolated by column chromatography as a mixture of two dia stereoisomersin the form of a semi-solid mass at room temperature.

Infrared absorptions (KBr disc.) were at: 3440, 3200, 1700, 1617, 1500,1450, 1370, 1239, 1145, 1074, 1050, 1005 and 740 cm⁻¹.

NMR spectrum [solvent DMSO-d6, internal standard Si(CH₃)₄ ] has signalsat: δ = 1.05 and 1.35 (singlet), δ = 2.02 and 2.14 (singlet), δ = 4.52and 4.57 (singlet), δ = 5.50 and 5.80 (broad signal), δ = 8.00 (broadsignal), δ = 6.1-6.4 (multiplet), δ = 7.35 and 7.50 (quartet).

The mass spectrum showed peaks at m/e 224, 128, 127, 97, 96, 95, 85, 57,43.

EXAMPLE XIV

A mixture of 2.0 g of 2,5-dimethyl-4-hydroxy-3-(2H)-furanone, 10 ml ofacetone and 25 ml of 6N hydrochloric acid was stirred at roomtemperature for 48 hours. After working up the reaction mixture, thecrude reaction product was purified by column chromatography. Elutionwith pentane-ether 90/10 yielded pure2-(2-hydroxy-2-propyl)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone.

Infrared absorptions were at (KBr disc.): 3480, 3380, 1700, 1686,1620(sh), 1610, 1470, 1460, 1445, 1383, 1370, 1256, 1210, 1182, 1118,1080, 1075, 1003, 969, 902, 860, 794, 750, 565, 325 and 318 cm⁻¹.

NMR spectrum [solvent DMSO-d6, internal standard Si(CH₃)₄ ] had signalsat: δ = 0.99 (singlet), δ = 1.12 (singlet), δ = 1.18 (singlet), δ = 2.05(singlet), δ = 4.32 (singlet), δ = 7.80 (broad signal).

The mass spectrum showed peaks at m/e 186, 171, 129, 127, 101, 97, 85,71, 59, 58, 57, 43. In an aprotic solvent the compound was fullyconverted to the furenidone upon heating at 160° C for 8 minutes.

EXAMPLE XV

To 200 g of a commercial available frying fat were added 15 mg of2-(1-hydroxy-4-cis-heptenyl)-2,5-dimethyl-4-hydroxy-3-(2H)-furanone andthe mixture was heated for 5 minutes at 150° C. This fat was unanimouslypreferred to the fat without addition by the flavour evaluation panel,because of its more sweet, butterlike character.

What is claimed is:
 1. A compound of the formula ##STR2## in which R¹and R² represent a C₁ -C₄ alkyl group, R³ represents hydrogen or amethyl group and R⁴ represents hydrogen or a C₁ -C₁₄ alkyl, a C₂ -C₁₀alkenyl, a benzyl, a furyl or an alkyl substituted furyl radicalcontaining up to 14 carbon atoms, with the proviso that R⁴ should notcontain more than 4 carbon atoms in case R³ represents a methyl group.2. A compound according to claim 1, in which R¹ and R² represent amethyl or an ethyl group.
 3. A compound according to claim 2, in whichR¹ and R² represent a methyl group.
 4. A compound according to claim 1,in which R⁴ represents a C₂ -C₁₀ alkyl radical.
 5. A process forpreparing a compound of the formula ##STR3## in which R¹ and R²represent a C₁ -C₄ alkyl group, R³ represents hydrogen or a methyl groupand R⁴ represents hydrogen or a C₁ -C₁₄ alkyl, a C₂ -C₁₀ alkenyl, abenzyl, a furyl or an alkyl substituted furyl radical containing up to14 carbon atoms, with the proviso that R⁴ should not contain more than 4carbon atoms in case R³ represents a methyl group, comprising reacting acompound of the formula ##STR4## with a carbonyl compound of the formula##STR5## in which R¹, R², R³ and R⁴ represent groups as indicated above,in a polar solvent in the presence of an acid catalyst.